Hipparion Macedonicum Revisited: New Data on Evolution of Hipparionine Horses from the Late Miocene of Greece

Hipparion macedonicum revisited: New data on evolution of hipparionine horses from the Late Miocene of Greece

GEORGE D. KOUFOS

Koufos, G.D. 2016. Hipparion macedonicum revisited: New data on evolution of hipparionine horses from the Late Miocene of Greece. Acta Palaeontologica Polonica 61 (3): 519–536.

The new expeditions to the Axios Valley (Macedonia, Greece) provided a new set of fossils from the various localities. Among the material collected from the Late Miocene hominoid bearing mammal locality Ravin de la Pluie (RPl) were some remains of Hipparion macedonicum, which was originally described from this locality. The most important is the skull and associated mandible, the first from the type locality. The new material is compared with the previously collected material of the taxon from the Vallesian and Turolian levels of Greece, as well as with corresponding material from Eurasia. The RPl skull is compared with the type skull of H. matthwei, a taxon, which several times has been referred as synonym to H. macedonicum. The comparison indicated several differences which distinguish the two species. Hipparion macedonicum has a continuous stratigraphic range from the Vallesian to middle Turolian and it is possibly present in the late Turolian. The comparison of the chronologically different samples of H. macedonicum indicates that the Vallesian form of H. macedonicum has larger size, shorter narial opening, longer tooth rows, rich enamel plication, more elongated and narrow plis, more robust metapodials and less running legs than the Turolian form. Some of the morphological changes are related to the habitat, which was more closed, warmer and wetter in the Vallesian than Turolian.

Key words: Mammalia, Equidae, systematic, evolution, palaeoecology, Miocene, Greece.

George D. Koufos [[email protected]], Aristotle University of Thessaloniki, Department of Geology, Laboratory of Geology and Palaeontology, GR-54124 Thessaloniki, Greece.

Received 20 April 2015, accepted 5 June 2015, available online 12 June 2015.

Copyright © 2016 G.D. Koufos. This is an open-access article distributed under the terms of the Creative Commons Attribution License (for details please see http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

new material of H. macedonicum from RPl is described and Introduction compared with the known material of the taxon from other localities in this article, providing information for its mor- The Late Miocene mammal locality Ravin de la Pluie (RPl, phology, relationships, evolution, as well as its stratigraphic Axios Valley, Macedonia, Greece) is well-known because and geographic distribution. of the presence of the hominoid primate Ouranopithecus macedoniensis. The RPl fauna is quite rich including mainly Institutional abbreviations.—AMNH, American Museum of mammals (Koufos 2006b, 2012a, b, and references cited Natural History, New York; LGPUT, Laboratory of Geology therein) and suggesting correlation to the late Vallesian (MN and Palaeontology, University of Thessaloniki, Greece. 10) with a magnetostratigraphically estimated age of ~9.3 Ma (Koufos 2013 and references cited therein). The hippar- Locality abbreviations.—AKK, Akkaşdağı, Turkey; DYTI, ions, in comparison to the Turolian localities, are rare in the localities of Dytiko 1, 2, 3, Axios Valley, Greece; DKO, Dytiko RPl sample and classified to two species: H. cf. H. sebas- 3, Axios Valley, Greece; KTA-B, Kemiklitepe-A, B, Turkey; topolitanum Borissiak, 1914 and H. macedonicum Koufos, KRY, Kryopigi, Greece; MTLA, Mytilinii-1A, Samos, 1984. The first taxon was described earlier as a form of H. Greece; MYT, Mytilinii-3, Samos, Greece; NIK, Nikiti-2, primigenium by Koufos (1986, 2000) but recently Vlachou Greece; NKT, Nikiti-1, Greece; PER, Perivolaki, Greece; PIK, (2013) transferred it to H. cf. H. sebastopolitamum; the other Pikermi, Greece; PXM, Prochoma 1, Axios Valley, Greece; taxon, H. macedonicum, was originally described from RPl Q1, Quarry 1, Samos, Greece; Q5, Quarry 5, Samos, Greece; (Koufos 1984, 1986). During the last expeditions in Axios RPl, Ravin de la Pluie, Axios Valley, Greece; RZ1, Ravin des Valley new material of H. macedonicum has been unearthed Zouaves 1 , Axios Valley, Greece; RZO, Ravin des Zouaves from RPl, including mainly mandibular remains but also 5, Axios Valley, Greece; SIN, Sinap, Turkey; TAR, Taraklia, the first skull, providing new information about the cranial Ukraine; PAV, Pavlodar, Kazakhstan; PNT, Pentalophos 1, morphology of H. macedonicum from the type locality. The Greece; VATH, localities of Vathylakkos, Greece.

Acta Palaeontol. Pol. 61 (3): 519–536, 2016 http://dx.doi.org/10.4202/app.00169.2015 520 ACTA PALAEONTOLOGICA POLONICA 61 (3), 2016

Other abbreviations.—DAP, antero-posterior diameter; mal part of McIII, LGPUT RPl-285; proximal part of tibia, HS, habitat score; KI, Keel Index; McIII , third metacarpal; LGPUT RPl-284; distal epiphysis of tibia, LGPUT RPl-288; MtIII, third metatarsal; PCA, principal component analysis; distal part of MtIII, LGPUT RPl-292. POF, preorbital fossa; POB, preorbital bar (length preorbital Emended diagnosis.—Small size; relatively elongated and fossa–anterior orbit); SI, Slenderness Index. narrow muzzle; shallow narial opening, the nasal notch is retracted above the middle of the C-P2 diastema; elliptical, shallow, antero-posteriorly oriented, not pocketed Material and methods posteriorly with moderately developed margin, and open anteriorly POF; moderate POB; infraorbital foramen en- The studied material, except the new collection, includes croaches upon the antero-ventral border of the POF; mod- also the old one described earlier (Koufos, 1984, 1986); all erate enamel plication in the upper cheek teeth with narrow studied material is housed in the Laboratory of Geology and and deep plis; simple-double pli caballin; elliptical-oval Palaeontology, University of Thessaloniki (LGPUT). The and isolated protocone; often connection of the fossettes; biometric study of the material follows the recommenda- very rare presence of a weak lingual hypoconal groove; tions of Eisenmann et al. (1988); all the measurements are often presence of functional dP1; elongated and slender given in mm with an accuracy of 0.1 mm. Upper and lower metapodials. case letters denote upper and lower teeth, respectively. The Hipparion matthewi differs from H. macedonicum hav- software PAST (Hammer et al. 2001) used for the princi- ing smaller size, shorter muzzle, deeper narial opening (na- pal component analysis (PCA) and box-plot diagrams and sal notch is retracted above the mesial half of P2), ovoid Office Excell 2010 for Simpson’s log-ratio diagrams. All with well-defined borders, deeper, dorso-ventrally oriented metrical data for the Greek material, as well as for those POF and infraorbital foramen situated in front but outside from Kemiklitepe A–B and Akkaşdağı are from author’s of POF. Hipparion nikosi differs from H. macedonicum database; those for Hipparion elegans and H. moldavicum are taken from www.vera-eisenmann.com. Hipparion med- having smaller size (similar to H. matthewi) and remarkably iterraneum from Pikermi was used as reference species deeper narial opening (nasal notch is retracted above the in the Simpson’s log-ratio diagrams and the measurements P3–P4) distinguishing it well from all known small hip- were taken from Koufos (1987). parions of the Eastern Mediterranean region. Hipparion moldavicum with larger size, longer muzzle, wider incisive row, deeper narial opening (nasal notch is retracted above or in front of P2), larger, deeper and posteriorly pocketed Systematic palaeontology POF, infraorbital foramen situated below the antero-ventral rim of POF and larger metapodials differs from H. mace- Family Equidae Gray, 1821 donicum. Hipparion sithonis Koufos and Vlachou, 2016 is Genus Hipparion de Christol, 1832 different in the slightly larger size, the deeper narial open- Hipparion macedonicum Koufos, 1984 ing (nasal notch is retracted above the mesostyle of P2), the Figs. 1–3. presence of canine fossa, the antero-ventrally oriented and with well-defined borders POF, and the relatively shorter 1980 Hipparion sp.; Koufos 1980: 292. 1984 H. macedonicum; Koufos 1984: 386, figs. 2, 3. and robust metapodials. Hipparion uzunagizli differs from 1986 H. macedonicum Koufos, 1984; Koufos 1986: 71, pls. 1–3. H. macedonicum in the longer and wider muzzle, the deeper 2013 H. macedonicum Koufos, 1984; Vlachou 2013: 318. narial opening (nasal notch is retracted above the mesial Type material: Holotype: mandible with i1–m3 dex and i1–m2 sin, margin of P2), the longer POB, the larger, subtriangular, LGPUT RPl-21 (Fig. 3A). Paratype: skull and associated mandible, antero-ventrally oriented and posteriorly pocketed POF. LGPUT RPl-125 (Figs. 1, 3C). Hipparion kecigibi with larger size, short and wider muzzle, Type locality: Ravin de la Pluie (RPl), Axios Valley, Macedonia, Greece. subtriangular, deeply pocketed posteriorly and larger POF is Type horizon: Late Vallesian, MN 10; Late Miocene; GPTS = ~9.3 Ma separated from H. macedonicum. Hipparion elegans differs (Koufos 2013 and references cited therein). in the larger size, the subtriangular with well-defined bor- Material.—The given list includes only the new unde- ders POF, the longer and wider snout, the longer tooth rows, scribed previously specimens. Skull and associated mandi- and the large and slenderer metapodials. ble, LGPUT RPl-125; right frontal part of the skull with the Measurements.—The measurements of the new material are muzzle and the tooth row, LGPUT RPl-142; left maxillary given in Supplementary Online Material (SOM: tables 1, 2) fragment with P3–M2, LGPUT RPl-287; partial mandible available at http://app.pan.pl/SOM/app61-Koufos_SOM.pdf. with i1–m2 dex and sin, LGPUT RPl-286; partial mandible with p2–m2 dex and p2–m3 sin, LGPUT RPl-290; left Fig. 1. Equid Hipparion macedonicum Koufos, 1984 (LGPUT RPl-125) → mandibular fragment with p2–m3, LGPUT RPl-281; right from Ravin de la Pluie, Axios Valley (Macedonia, Greece), late Vallesian, mandibular fragment with p2–m3, LGPUT RPl-282; left MN 10 (Late Miocene). A–D. Skull in right (A) and left (B) lateral, later- mandibular fragment with p2–p4, LGPUT RPl-291; proxi- al-dorsal (C), and ventral (D) views. E. Left tooth row in occlusal view. KOUFOS—LATE MIOCENE HORSES FROM GREECE 521 522 ACTA PALAEONTOLOGICA POLONICA 61 (3), 2016

Fig. 2. Equid Hipparion macedonicum Koufos, 1984 from Ravin de la Pluie, Axios Valley (Macedonia, Greece), late Vallesian, MN 10 (Late Miocene). A. LGPUT RPl-142, right frontal part of skull in lateral (A1) and occlusal (A2) views, right tooth row in occlusal view (A3). B. LGPUT RPl-37, left tooth row in occlusal view. Description.—LGPUT RPl-125 is a partially preserved impression that it is very narrow. The choanae are narrow skull lacking the occipital part (Fig. 1A–D); its left side is and their anterior margin is at the middle of M1. better preserved (the ventral and distal part of the orbit and The upper cheek tooth row is well preserved, short and the zygomatic arch are preserved) than the right one which moderately worn in all studied specimens; in LGPUT RPl-142 is more damaged. The skull is laterally compressed and the it is unworn-little worn (IId stage; the M3 is erupted) (Figs. dimensions are slightly influenced being smaller. The muz- 1E, 2A3, B). The tooth rows of LGPUT RPl-125 and LGPUT zle is relatively elongated and narrow; the narial opening is RPl-142 preserve a functional dP1. The P2 has a short and shallow; the nasal notch is retracted above approximately ½ rounded anterostyle, well separated from the protoloph and of the distance between the canine and P2. The incisive row connected fossettes in all specimens, except LGPUT RPl-37 is rounded and all incisors are well developed. The bucci- (Fig. 2B). The enamel in the fossette’s borders is plicated and nator fossa is very deep and pocketed posteriorly. The POF the plis are elongated and moderately deep; this morphology is better preserved in LGPUT RPl-142 (Fig. 2A1) and in the is clear in the moderately worn teeth of LGPUT RPl-37. The right side of LGPUT RPl-125 (Fig. 1A). It is elliptical, shal- mean plication number ranges between 7–17 (mean 14.1) in low, antero-posteriorly oriented, not pocketed posteriorly the premolars and 10–17 (mean 13.6) in the molars. The pli with moderately developed margin, and open anteriorly. caballin is single in all teeth, except LGPUT RPl-37 where The infraorbital foramen encroaches upon the antero-ven- it is double in the premolars. The protocone is isolated in all tral border of the POF. The partially preserved right orbit of teeth, rounded-oval in the premolars and oval-lenticular in the LGPUT RPl-125 indicates that the POB is probably moder- molars; a weak spur occurs in the little worn teeth of LGPUT ate and the mesial orbital margin is situated above the mid- RPl-142 (Fig. 2A3, B). The hypocone is elliptical-angular but dle of M3. The palate is laterally compressed and gives the it is rounded in M3 of all specimens. The distal hypoconal KOUFOS—LATE MIOCENE HORSES FROM GREECE 523 groove is deep in the less worn teeth and shallower in the more worn ones. In all M3 there is a deep lingual hypoconal groove separating well the hypocone while a very weak lingual hypoconal groove occurs in some teeth. Although the mandible and the lower teeth of H. macedonicum from RPl have been described earlier on the basis of the holotype LGPUT RPl-21 and LGPUT RPl-17, the five new mandibles (LGPUT RPl-125, 281, 282, 286, 290) add more data (Fig. 3). The mandible relative to its size has high mandibular corpus; its height is remarkably reduced and became small in front of p2. The snout is relatively elongated and narrow. The incisive row is rounded and narrow between the distal margins of the i3s; in LGPUT RPl-125 seems to be wide but this is due to a strong dorso-ventral compression and deformation which flattened the incisive area. The symphysis is relatively short, like in the holotype LGPUT RPl-21. The lower teeth are well preserved in most of the available mandibles (Fig. 3). The paraconid of the p2 is elongated and projects mesially. The parastylid is open mesially in the less worn teeth but it is closed and joined with the protostylid in the much worn ones (LGPUT RPl-17). The protostylid is moderately high occurred in the half-worn teeth; it is well distinguished in LGPUT RPl-17, 125, 290, while in the holotype LGPUT RPl-21 just appeared and it is clearly separated from the parastylid. The metaconid is elliptical-rounded in the premolars, and rounded in the molars. The linguaflexid is open, V-shaped and deep touching the ectoflexid in the worn and much worn teeth. The ectoflexid is narrow and very deep, especially in the molars. The metastylid is elliptical in the premolars and more rounded in the molars. There are plications or crenulations in the preflexid and postflexid enamel which gradually disappear by the attrition. The postcranial remains of H. macedonicum from RPl are a few; except those desribed earlier (Koufos 1984, 1986), the new material includes some bone fragments, the size of which correlates them to the RPl small-sized hiparion. Remarks.—Hipparion macedonicum was originally described on a small suite of mandibles, maxillary fragments and post cranial remains from RPl (Koufos 1984, 1986) but soon it was recognized in several localities of Axios Valley (PNT, RZ1, RZO, PXM, VATH) and later in Nikiti (NKT, NIK), as well as in Perivolaki (PER) (Koufos 1987b, c, 1988, 2000; Vlachou and Koufos 2002, 2006; Koufos and Vlachou 2016). The cranial characters of the taxon are mainly known from an almost complete skull from the Turolian locality PXM and Fig. 3. Equid Hipparion macedonicum Koufos, 1984 from Ravin de la some partial skulls from the other Turolian localities of north- Pluie, Axios Valley (Macedonia, Greece), late Vallesian, MN 10 (Late ern Greece (Koufos 1987c, 1988; Vlachou and Koufos 2006; Miocene). A. Holotype LGPUT RPl-21, mandible in right lateral (A1) and occlusal (A2) views. B. LGPUT RPl-286, mandible in right lateral (B1) and Koufos and Vlachou 2016). LGPUT RPl-125, as it originates occlusal (B ) views. C. LGPUT RPl-125, mandible in left lateral (C ) and from the type locality, allows to study the cranial morphology 2 1 occlusal (C2) views. of H. macedonicum in its typical site, as well as to see its evolutionary relationships with the younger forms of the species, separates well the various Hipparion taxa according to their and other small-sized hipparions. size (Fig. 4A). The small-sized hipparions match in the The mean values of the RPl cranial and mandibular lower and the medium-sized ones in the upper half of the remains are compared with the corresponding ones of H. PC2, while the very small and large forms are displayed macedonicum from other localities, as well as with other in the two extremes of the PC1. The RPl skull matches H. Hipparion taxa known from Eurasia. The PCA for the skull macedonicum suggesting that metrically is very close to 524 ACTA PALAEONTOLOGICA POLONICA 61 (3), 2016

Fig. 4. Principal component analysis of the skull (A), mandible (B), and third metatarsal (C) of the RPl small-sized hipparion in comparison with other small-sized forms of Eurasia, indicating its strong size-similarities with Hipparion macedonicum. As the available specimens are fragmentary, lacking measurements the mean cranial dimensions for each locality are used. The used variables (various measurements of the skull, mandible and MtIII) and their influence to the distinction of the specimens is given in the left part of the diagrams. The convex hulls indicate the allocation of the measurements in the space for its sample. Hipparion dietrichi, Hipparion mediterraneum, and Hipparion proboscideum or Hipparion cf. proboscideum are used as comparative samples. Hipparion macedonicum: 1, NKT; 2, NIK; 3, RZO; 4, PXM; 5, VATH; 6, PER. Hipparion matthewi: 7, Samos (unknown locality), holotype; 8, KTA-B. Hipparion cf. matthwei: 9, MTLA. Hipparion sithonis: 10, NIK. aff. Hipparion forstenae: 11, MTLA; 12, Samos Q1. Hipparion → KOUFOS—LATE MIOCENE HORSES FROM GREECE 525 this taxon. The type of H. matthewi Abel, 1926 and the locality PER differs from the RPl one in the longer muzzle skulls described as H. cf matthewi are well separated from and palate (this difference is artificial; as it was referred in the RPl skull being quite smaller. Three other small-sized the description the deformation of the skull LGPUT RPl-125 species have skulls comparable in size to the RPl one (Fig. affects the palate breadth), as well as the shorter tooth rows 4A). Hipparion elegans Gromova, 1952 differs from the RPl (Fig. 5A: measurements 1, 2, 7–9). A partial skull from the in several morphological features (see below). The other late Turolian locality DKO, reported as H. cf. macedonicum two are H. sithonis Koufos and Vlachou, 2016 and aff. H. by Vlachou (2013), has similarities with the RPl skull but it forstenae Zhegallo, 1971 and both are separated from H. differs from it in the wider muzzle and shorter tooth rows macedonicum and RPl skull having canine fossa. The PCA (Fig. 5A: measurements 2, 7–9, 15). Taking in mind the for the mandible, although the distinction of the various taxa Vallesian age of the RPl, there is a trend in H. macedonicum is not sufficient, the RPl mandible is closer to H. macedon- for reduction of the tooth rows, increase of the narial opening icum and H. sithonis than to H. matthewi which has smaller depth, and increase of the muzzle width from Vallesian to mandible (Fig. 4B). Turolian. The mandible LGPUT RPl-125 has similar mor- The MtIII sample of the various species is rich and can phological characters to the holotype of H. macedonicum allow a good comparison. The PCA separates well the MtIII (LGPUT RPl-21). In mean values the RPl mandible has sim- of the various taxa according to their mid-shaft length and ilar proportions to H. macedonicum from the various locali- width (Fig. 4C). The RPl MtIII is into the area of H. mace- ties (Fig. 6A). However, the NIK mandible seems to have less donicum and can be referred to it; however, it is clear that high mandibular corpus than those from the other localities; there is a great overlapping between the various taxa e.g. the this is artificial and possibly due to the fact that these mea- MtIII of H. macedonicum and H. sithonis cannot be distin- surements (Fig. 6A: measurements 10–12) come from a sin- guished, as they overlap each other (Fig. 4C). The distinc- gle and badly preserved mandible from NIK. The RPl MtIII tion of hipparions having similar size and the attribution has similar proportions to H. macedonicum from the other of the postcranials to the one or the other taxon (except localities but it is slightly longer with smaller articular facet having complete skeletons) is, in most cases, arbitrary. The for the cuboid (IV tarsal), (Fig. 7A: measurements 1, 8). The correlation is mainly based on size or some morphological DYTI MtIII, though its proportional similarity to H. mace- features, if there are, e.g., H. macedonicum and H. sithonis donicum, it is remarkably smaller than the RPl one (Fig. 7A). are well-separated by their skull morphology (presence or Hipparion matthewi.—It is a small-sized hipparion origi- absence of canine fossa) but the distinction of the postcra- nally described on a skull and associated mandible from an nial remains is difficult or even impossible. The presence of unknown locality of Samos. A direct comparison of LGPUT two hipparions in RPl, a large- and a small-sized one makes RPl-125 with a cast of the holotype (LGPUT OK/557), in- the distinction of the postcranials easier, but we cannot ex- dicated that LGPUT RPl-125 differs from H. matthewi hav- clude the possibility of a second large or small hipparion in ing: larger size (Figs. 4A, 5B, 6B); longer muzzle (Fig. 5B: the sample. measurement 1); less deep narial opening, the nasal notch is retracted above the middle of the C-P2 diastema, while in OK/557 is above the mesial half of the P2; shorter palate Comparisons (Fig. 5B: measurement 2); both skulls are laterally compressed and may be this difference is not so indicative; mor- Hipparion macedonicum.—As it is mentioned above H. phologically different POF, in LGPUT OK/557 it is ovoid macedonicum is reported from several Vallesian and Turolian with well-defined borders, deeper, dorso-ventrally oriented localities of Greece. The RPl skull has similar proportions to and the infraorbital foramen is situated in front of the POF (but outside of it); longer snout (Fig. 6B: measurement 2). an almost complete skull from the middle Turolian locality Hipparion matthewi is reported from the middle Turolian PXM (Fig. 5A). The differences are limited and restricted localities Kemiklitepe A–B (KTA–B) of Asia Minor by to the slightly longer and wider muzzle, the shorter tooth some mandibular and postcranial remains (Koufos and rows, the wider incisive row, and the slightly deeper nar- Kostopoulos 1994; Vlachou 2013). The KTA-B mandible ial opening (Fig. 5A: measurements 1, 7–9, 14, 15, 30). A has similar proportions to the type of H. matthewi. It differs set of cranial remains of H. macedonicum, described from from the RPl one in the shorter and narrower snout and the the early Turolian locality NIK (Koufos and Vlachou 2016) slightly shorter premolar row (Fig. 6B: measurements 2, 4). differs from the RPl skull in the shorter and wider muzzle The KTA-B metatarsal is slightly shorter, wider in the mid- and the shorter tooth rows (Fig. 5A: measurements 1, 7–9, shaft with smaller distal epiphysis than the RPl one (Fig. 7B: 15). The skull of H. macedonicum from the Middle Turolian measurements 1, 3, 11–14). The small-sized hipparions of Eastern Mediterranean elegans: 13, PAV. Hipparion moldavicum: 14, TAR; 15. AKK. Hipparion philippus: 16, NIK; 17, RZO; 18, PXM; 19, VATH; 20, PER. Hipparion region were reported as H. matthewi or H. cf. matthewi for dietrichi: 21, MTLA; 22, MTLB; 23, Samos Q4; 24, Samos Q1. Hipparion a long time. Most of them have significant differences from mediterraneum: 25, PIK. H. proboscideum: 26, Samos Qx; 27, MTLA; 28, the type of H. matthewi (e.g., some skulls from Q5 of Samos Samos Q1. Hipparion cf. proboscideum: 29, PER. interpreted as H. matthwei by Sondaar (1971) are different 526 ACTA PALAEONTOLOGICA POLONICA 61 (3), 2016

Fig. 5. Logarithmic ratio diagram comparing the RPl skull with Hipparion macedonicum and other small-sized hipparions from various localities. Hipparion mediterraneum from Pikermi (Koufos 1987a) is used as standard of comparison. The metrical data for the hipparions from Greek localities and AKK are from author’s archive; those for Hipparion moldavicum from TAR and H. elegans from PAV are taken from http://www.vera-eisenmann.com. and remarkably larger than the type skull). In my opinion, material needs revision or it is limited for certain determi- except the type skull and mandible of H. matthewi, all the nation. The revision of the Sondaar’s (1971) cranial material rest material, attributed to this taxon or described as H. cf. described as H. matthewi indicated that it belongs to H. matthewi could belong or not to H. matthewi but either the nikosi (very deep narial opening) and to H. cf. dietrichi, KOUFOS—LATE MIOCENE HORSES FROM GREECE 527

Fig. 6. Logarithmic ratio diagram comparing the RPl mandible with Hipparion macedonicum and other small-sized hipparions from various localities. Hip- parion mediterraneum from Pikermi (Koufos 1987a) is used as standard of comparison. The metrical data for the hipparions from Greek localities and AKK are from my own archive; those for Hipparion moldavicum from TAR and Hipparion elegans from PAV are taken from http://www.vera-eisenmann.com. while the fragmentary specimens and the postcranial re- Hipparion sithonis.—It is a new small-sized hipparion de- mains potentially can belong to any small- to medium-sized scribed from the early Turolian locality NIK (Koufos and hipparion (Vlachou and Koufos 2006, 2009; Vlachou 2013). Vlachou 2016). The presence of the canine fossa in H. si- Thus, it is necessary to define first the taxonomic status of thonis differentiates it from the RPl skull. Its size is similar H. matthewi (the only certain specimen is the holotype) by to the RPl form but it differs from it in the longer palate, finding new material in the Samos localities. Unfortunately, shorter tooth rows, deeper narial opening (the nasal notch is we could not find such a small-sized hipparion during our retracted well behind the mesostyle of the P2), wider and an- recent excavations in Samos (Vlachou and Koufos 2009). tero-ventrally oriented POF (Fig. 5A: measurements 2, 7–9, 528 ACTA PALAEONTOLOGICA POLONICA 61 (3), 2016

Fig. 7. Logarithmic ratio diagram comparing the RPl third metatarsal with Hipparion macedonicum and other small-sized hipparions from various localities. Hipparion mediterraneum from Pikermi (Koufos 1987a) is used as standard of comparison. The metrical data for the hipparions from Greek localities and AKK are from my own archive; those for Hipparion moldavicum from TAR and Hipparion elegans from PAV are taken from http://www. vera-eisenmann.com. 30) and longer snout. The metatarsal of H. sithonis, though Hipparion nikosi.—H. nikosi Bernor and Tobien, 1989 is a its proportions are similar to the RPl one, it is shorter with small-sized hipparion from Samos (unknown locality) char- larger articular facet for the fourth tarsal (cuboid) than the acterized by a very deep narial opening, the nasal notch is RPl one (Fig. 7B: measurements 1, 8). retracted above the P4 (Bernor and Tobien 1989). Recently KOUFOS—LATE MIOCENE HORSES FROM GREECE 529

A 0.25

0.15 RPI mean 0.05 H. macedonicum, NIK (n, 1 9)– H. macedonicum, PXM (n, 1 9)– -0.05 H. macedonicum, PER (n, 1 20)– H. sinapensis, SIN (n, 1 2)– -0.15 H. uzunagizli, SIN (n, 1 3)–

Log differences H. kecigibi, SIN (n, 1) -0.25

-0.35 1 2 7 8914 15 30 33 34 35 36 37 38

B 0.10

0.05

RPI mean 0.00 H. macedonicum, PNT (n, 1) H. macedonicum, RZ1 (n, 1) -0.05 H. sinapensis, SIN (n, 4) H.aff. uzunagizli , SIN (n, 2) -0.10

Log differences H.aff. kecigibi, SIN (n, 4 – 5)

-0.15

-0.20 1 3 456 10 11 12 13 14 7 8 Fig. 8. Logarithmic ratio diagram comparing the RPl skull (A) and third metatarsal (B) with the Vallesian hipparions from Sinap, Turkey. Hipparion mediterraneum from Pikermi (Koufos 1987a) is used as standard of comparison. The metrical data for the Sinap material were provided to me by Raymond L. Bernor (unpublished material, personal communication, 2007).

Vlachou (2013) reported some skulls (AMNH 22888, 22907, Hipparion moldavicum.—It is a small- to medium-sized 22936, 22908) from Q5 of Samos, to this species. The size hipparion known from Taraklia (Ukraine) but later it was of H. nikosi skull is close to that of the RPl form but it recognized in the wider Black Sea region, Turkey and differs from it in the slightly longer palate, shorter tooth Iran (Bernor 1985; Watabe and Nakaya 1991; Watabe rows and deeper narial opening (Fig. 5B: measurements 2, 2004; Koufos and Vlachou 2005). Hipparion moldavicum 7–9, 30). The metapodials from Q5, attributed to H. nikosi Gromova, 1952 is larger than the RPl form (Figs. 5C, 6C) by Vlachou (2013) are proportionally very close to the RPl having deeper narial opening (in the AKK skulls the nasal form as well as to those of H. macedonicum from the other notch is retracted above the P2), weak posterior pocketing localities (Fig. 7A, B). of the POF, infraorbital foramen below the antero-ventral Hipparion elegans.—The small-sized H. elegans Gromova, border of the POF, longer snout, wider incisive row, and lon- 1952 is originally described from Pavlodar, Kazakhstan ger symphysis (Figs. 5C, 6C).The MtIII of H. moldavicum is (Gromova 1952) and it is reported as synonym of H. mat- quite larger than those of the RPl ones (Fig. 7C). thewi or closer to H. moldavicum Gromova, 1952 (Forstén Sinap hipparions.—Bernor et al. (2003) described a num- 1968, 1997; Pesquero et al. 2011). The skull of H. elegans ber of new hipparions from the Vallesian deposits of Sinap, differs remarkably from the RPl one in the longer palate, as Turkey on the basis of their cranial remains. All are larger well as the size and position of the POF (Fig. 5C: measure- than H. macedonicum (Fig. 8A). Hipparion sinapensis ments 2, 33, 35, 36, 38). Based on the figures of Gromova Bernor, Scott, Fortelius, Kappelman, and Sen, 2003 from (1952) its POF is sub-triangular with well-defined borders. the early Vallesian, MN 9 (10.55–9.97 Ma) of Sinap is sep- The mandible has longer and wider snout, longer tooth rows, arated from H. macedonicum by the longer muzzle, longer and remarkably longer symphysis (Fig. 6C: measurements palate, longer tooth rows, longer POB (~41 mm), as well as 2, 3–5, 13). The metatarsal of H. elegans is slenderer with the subtriangular, antero-ventrally oriented, deeply pock- larger proximal articular surfaces than the RPl one and H. eted posteriorly, and situated closer to the facial crest POF macedonicum from the other localities (Fig. 7C). (Fig. 8A: measurements 1, 7–9, 36). The MtIII of H. mace- 530 ACTA PALAEONTOLOGICA POLONICA 61 (3), 2016 donicum has similar length but it is more slender than that of Fig. 9). Earlier Eisenmann (1988) recognized a small-sized H. sinapensis (Fig. 8B). Hipparion uzunagizli Bernor, Scott, hipparion in the late Vallesian locality of Montredon, France Fortelius, Kappelman, and Sen, 2003, known from the early and described it as H. cf. macedonicum. Based on the data, Vallesian, MN 9 (9.967–9.918 Ma) of Sinap differs from H. from the Greek localities H. macedonicum has a continuous macedonicum in the longer and wider muzzle, the deeper na- presence in the Late Miocene faunas of Europe (Fig. 9). rial opening (nasal notch retracted above the mesial margin Vlachou (2013) considered that H. macedonicum could be of the P2), the more far situated orbit, the remarkably longer synonym to (i) “H. minus” Pavlow, 1890 from Sebastopol, POB, the subtriangular, antero-ventrally oriented, and pos- Moldavia dated to early Vallesian, MN 9 (Vangengeim and teriorly pocketed POF, as well as the more robust metatarsal Tesakov 2013); (ii) Hipparion sp. from Sumeg, Hungary (Fig. 8B: measurements 1, 2, 15, 30). On the other hand, dated to late Vallesian, MN 10 (Bernor et al. 1999); and (iii) the two species have some similarities as the tooth rows H. cf. macedonicum from Montredon, France dated to late length (slightly larger in H. uzunagizli; Fig. 8A), the shape Vallesian, MN 10 (Eisenmann 1988). If this hypothesis is of the POF and the presence of a functional dP1. Bernor et true and taking in mind its possible presence in Bulgaria, al. (2003) mentioned that the POF of H. uzunagizli is going the taxon appeared or arrived in southeastern Europe in the to be egg-shaped with antero-posterior orientation and re- early Vallesian (MN 9) and migrated to Central and Western duced size being closer to that of H. macedonicum in which Europe, where it was found in the late Vallesian (MN 10). it is elliptical, reduced and antero-posterioly oriented. The The above comparisons of H. macedonicum from the third hipparion from the early Vallesian, MN 9 (9.683 Ma) various fossiliferous sites, from a first point of view, indicate of Sinap is H. kecigibi Bernor, Scott, Fortelius, Kappelman, some intraspecific changes related to the time. We shall try and Sen, 2003, separated from H. macedonicum in the short to check these changes and how they are related. Looking and relatively very wide muzzle, the longer tooth rows, the to the diagrams of Figs. 5–7 it is clear that there are some deep posterior pocketing of POF and the remarkably more changes in H. macedonicum from Vallesian to Turolian. robust metatarsals (Fig. 8). The two taxa have similar depth of the narial opening (Fig. 8A: measurement 30), as well as Body mass.—The body mass is a good size indicator for elliptical-subtriangular shaped, antero-posteriorly oriented, the equids and it is related to the size of the metapodials. and moderately deep POF. Both H. uzunagizli and H. keci- The main variables used for its estimation are the distal gibi shared some morphological characters with H. mace- maximal suprarticular breadth and the distal minimal depth donicum indicating close relationships. of the lateral condyle (Scott 1990; Eisenmann and Sondaar 1998). On the other hand, Alberdi et al. (1995) estimated the body mass of the equids using the proximal DAP of the first Discussion phalanx. As the phalanges are absent in RPl and the other Vallesian localities, the body mass estimation is based on Hipparion macedonicum is common in the Late Miocene metapodials using the following formulas of Eisenmann and of Greece with a continuous occurrence in the deposits of Sondaar (1998) which show the highest R-values: Axios Valley (Macedonia, Greece). The oldest known oc- W1. ln(body mass) = -5,768+3.011 × (lnMc10) R = 0.94 currence of H. macedonicum is traced in PNT and correlated W2. ln(body mass) = -3.152+2.665 × (lnMc13) R = 0.92 to the early Vallesian, MN 9 (Fig. 9). The peculiar character W3. ln(body mass) = -4.525+1.434 × (ln(Mc10 × Mc13)) R = 0.94 of the PNT fauna, in comparison to the other ones of Axios W4. ln(body mass) = -4.362+2.634 × (lnMt10) R = 0.93 Valley, was early recognized and an early Vallesian (MN 9) W5. ln(body mass) = -4.552+3.100 × (lnMt13) R = 0.94 age speculated (Koufos 2013 and references cited therein). W6. ln(body mass) = -4.585+1.443 × (ln(Mt10 × Mt13)) R = 0.94 The early Vallesian age of PNT was confirmed by the presence of Choerolophodon anatolicus (Ozansoy, 1965) char- The body mass is calculated for each metapodial with all acterizing early Vallesian (Konidaris et al. 2016). The last formulas and then the mean value for each used variable and occurence of H. macedonicum is reported from PER (Fig. sample is given in Fig. 10. Vlachou and Koufos (2002) men- 9), dated to the upper part of the middle Turolian (upper MN tioned that the body mass of H. macedonicum decreases in 12), at about 7.3–7.1 Ma (Koufos et al. 2006b). The taxon is relation to the time. In fact, the mean body mass of H. mace- possibly present in the late Turolian, MN 13 localities DYTI donicum decreases from Vallesian to the end of Turolian of Axios Valley (Fig. 9). It is described as H. cf. macedon- with the youngest H. cf. macedonicum from DYTI having icum by Vlachou (2013) and it is smaller than the typical the smaller body mass than all other forms (Fig. 10) con- H. macedonicum with some differences mentioned above firming the above hypothesis. The body mass for the NKT but the limited and badly preserved material cannot allow H. macedonicum is similar to the Turolian forms and this is confirming its confident presence. A small-sized hipparion probably due to its younger age (terminal Vallesian; Koufos from the Bulgarian localities Kocherinovo 2 and Kalimantsi et al. 2016). The mean body mass for the Vallesian H. mace- 1 was described as H. cf. macedonicum and H. gr. macedonicum ranges between 72.3–121 kg, between 49.5–94.7 kg donicum respectively; both localities are correlated to early for the early–middle Turolian form, and between 56.9–67.5 Turolian, MN 11 (Spassov et al. 2006; Hristova et al. 2013; for the late Turolian form). Exceptionally the W2 mean value KOUFOS—LATE MIOCENE HORSES FROM GREECE 531

Fig. 9. Stratigraphic table indicating the distribution of Hipparion macedonicum in Europe. The geomagnetic time scale is from Cande and Kent (1995). The shaded area in the MN zones express the different opinions for the MN 12/13 boundary; according to Sen (1997) it is at ~7.0 Ma while according to Steininger et al. (1999) it is at ~6.6 Ma. of VATH H. macedonicum is high (107.2 kg) but such high is given by the plication number which is the sum of plis in W2 values are also observed in the NIK and PER sample. the fossette borders and pli caballin. The plication number Tooth row length.—The length of the tooth rows is a variable for the upper cheek teeth of H. macedonicum from the vari- also related to the size of the equids and it is used for com- ous sites decreases from the Vallesian to Turolian (Fig. 12), suggesting a habitat change to more open and dry conditions. parisons between them. The length for the upper and lower tooth rows of H. macedonicum from the various localities is Slenderness and keel development.—The equid metapo- given in the Box-plot diagrams of Fig. 11. Although the data dials are also indicative for their habitat. Eisenmann (1995) from the Vallesian localities are limited, restricted only in the following Gromova (1952) linked the gracility of the metap- RPl sample, it is clear that the mean length of the tooth rows odials, expressed by the Slenderness Index (SI), to open and/ is higher in the Vallesian than Turolian forms of H. macedon- or dry conditions. On the other hand, Gromova (1952) and icum, indicating a related to the time size reduction (Fig. 11). Scott (2004) linked the metapodial diaphysis to the hipparion habitat. The SI is equal to the result of the distal maximal Enamel plication.—The enamel plication of the upper cheek articular breadth divided by the maximal height of the meta- teeth of hipparions is a variable related to their feeding pref- podials (Gromova 1952; Eisenmann 1995). Besides the lim- erences and consequently to the environment. Gromova ited sample of the Vallesian metapodials there is a trend for (1952) related the low enamel plication with hard food and a gradual reduction of SI from Vallesian to Turolian forms of relatively open habitat while the rich enamel plication sug- H. macedonicum (Fig. 13A, B). This is in accord to the corre- gests soft food and closed habitat. Forstén (1968) considered sponding gradual reduction of the body mass (Fig. 10) as the that the forest hipparions are characterized by deep, narrow heavier (large-sized) forms need more robust metapodials to and almost parallel plications in the fossette borders which carry their weight. The size of the sagittal keel in the distal allow the broken up of soft food (herbs, leafs) but not those articular surface of the metapodials is related to their lateral of hard particles because the intervening space between the mobility, the larger sagittal keel the less mobility of the meta- enamel lamellae is very narrow. In contrast the enamel plis of podials and the more expressed running character of hippar- the hipparions, living in open habitats, are fewer, irregular, ion (Eisenmann 1995). The development of the sagittal crest short and the single plis wide allowing a large intervening is expressed by the Keel Index (KI) which is the quotient of space between them; this pattern supports the grinding of the distal maximal DAP of the keel by the distal minimal tough grass rich in silica. The enamel plication of the teeth depth of the lateral condyle. The KI of H. macedonicum 532 ACTA PALAEONTOLOGICA POLONICA 61 (3), 2016

Fig. 10. Body mass of Hipparion macedonicum from the various Greek localities calculated by various methods and its change in relation to the time. The body mass is estimated using the metapodials (Eisenmann and Sondaar 1998); W1. ln(body mass) = -5,768+3.011 x (lnMc10); W2. ln(body mass) = -3.151+2.665 x (lnMc13); W3. ln(body mass) = -4.525+1.434 x (ln(Mc10 x Mc13)); W4. ln(body mass) = -4.362+2.634 x (lnMt10); W5. ln(body mass) = -4.552+3.100 x (lnMt13); W6. ln(body mass) = -4.585+1.443 x (ln(Mt10 x Mt13)).

P2 M3– p2–m3 A 132 B127 5. 129 125.0 126 * 122 5. 123 120.0 120 117. 5 117 115.0 114 112. 5 111 110.0 108 107 5.

Tooth row length (mm) Tooth row length (mm) 105.0 RPI NIK RZO PXM PER DYTI RPI NIK RZO PXM VATH PER DYTI C P2 P4– D 78 68 p2 p4– 75 66 72 64 69 62 66 * 60 63 58 60 56 57 54 54 52 51

Premolar row length (mm) Premolar row length (mm) 50 RPI NIK RZO PXM PER DYTI RPI NIK RZO PXM VATH PER DYTI E M1 M3– F m1 m3– 60 68 58 66 56 64 62 54 Fig. 11. Box-plot diagrams comparing the 60 52 58 length of the upper and lower tooth row 50 56 (A, B), premolar row (C, D), and molar 48 54 row (E, F) of Hipparion macedonicum 52

Molar row length (mm) Molar row length46 (mm) 50 from the various Greek localities. RPI NIK RZO PXM PER DYTI RPI NIK RZO PXM VATH PER DYTI from the various fossiliferous sites increases from Vallesian habitats while positive values indicate open ones; values be- to Turolian (Fig. 13C, D) suggesting less lateral mobility and tween them indicate habitats with heavy or light cover. The more running character for the Turolian forms of the taxon calculated HS for the various forms of H. macedonicum sug- indicating more open conditions than in the Vallesian. Scott gest heavy-light cover habitat for it (Fig. 14). (2004), based on the older idea of Gromova (1952) that the The analysis of the palaeoecological characters of H. equid metapodials reflect the habitat, suggested the habitat macedonicum from the various Late Miocene sites of Greece score (HS) as a palaeocological indicator depending upon indicated that they significantly changed from Vallesian the metapodial variables. Negative HS corresponds to closed to Turolian suggesting in fact different habitats. The Late KOUFOS—LATE MIOCENE HORSES FROM GREECE 533

Fig.12. Plication number of the upper cheek teeth of Hipparion macedonicum from the various Greek localities.

Fig. 13. Slenderness and Keel indexes for the third metacarpal (A, B) and metatarsal (C, D) of Hipparion macedonicum from the various Greek localities. Dots indicate outliers. Miocene palaeoenvironment of northern Greece was deter- itat scores of H. macedonicum metapodials which suggest a 18 mined using various parameters, such the comparison of the heavy-light cover habitat (Fig. 14). The δ Op values of apatite fossil mammal faunas with modern ones, dental microwear, phosphate in the teeth of hipparions from northern Greece and isotope analysis of the enamel. All data suggested: (i) suggest a mean air temperature increasing from 13±3°C to open, dry and warm habitat similar to the modern savannah 17±2°C during late Vallesian–middle Turolian. The mean like ones (savannah bushland, grassland, gallery forests or annual precipitation, during the same time interval, reduced (+109 -1 (+58 -1 mixed) and (ii) less dry and warm conditions in the Vallesian from 890 -100) mm a to 471 -54) mm a (Rey et al. than the Turolian (Bonis et al. 1992; Koufos 2006a; Koufos 2013). In addition, extensive studies in the wider Eastern et al. 2006a, 2009a, 2016; Kostopoulos 2009; Merceron et Mediterranean region confirm the open, warm and dry char- al. 2005, 2007; Konidaris et al. 2016). The open character acter of the palaeoenvironment during Late Miocene (Bonis of the Late Miocene habitat is also confirmed from the hab- et al. 1992; Koufos 2006a; Strömberg et al. 2007; Merceron 534 ACTA PALAEONTOLOGICA POLONICA 61 (3), 2016

photype reporting its close relationships to H. moldavicum. In fact the relatively elongated and narrow muzzle, the shallow narial opening, the antero-posteriorly oriented with reduced posterior pocketing of the POF, the moderate-high enamel plication of H. macedonicum are primitive characters observed in H. moldavicum and confirm their relationship. The morphology of LGPUT RPl-125 is in accord to these observations and confirms them. Vlachou (2013) also noted the reduction of the POB and the metapodial gracility, characters appeared in the early Vallesian (MN 9) H. uzunagizli from Sinap Tepe, Turkey and increased in H. macedonicum which seems to be more derived with smaller size, shallower POF, absence of posterior pocketing in POF and slenderer metapodials. The possible relationships of H. macedonicum and H. uzunagizli are also mentioned in the comparisons. Taking in mind the size reduction and increase of the metapodial slenderness of H. macedonicum with the time, the PNT form of H. macedonicum could be similar to H. uzunagizli. This is in contrast to the fact that the metapodials of the PNT H. macedonicum are similar to the RPl and RZ1 ones, while those of H. uzunagizli are closer in size to those of H. moldavicum (Figs. 7C, 8B) but this is probably due to the PNT and Sinap limited material. The morphology of H. macedonicum is closely related to H. moldavicum and it is quite possible to derive from this taxon as it is proposed earlier (Bernor et al. 1996; Koufos and Vlachou 2005; Vlachou 2013).

Fig. 14. Habitat scores for the third metacarpals (A) and metatarsals (B) Conclusions of Hipparion macedonicum from the various Greek localities; the habitat scores are calculated following Scott (2004). Dots indicate outliers and The new material of H. macedonicum from the type local- asterisks single specimens. ity, especially the skull and associated mandible, provided interesting data for this species. Hipparion macedonicum et al. 2004, 2006, 2016; Eronen et al. 2009; Kostopoulos is usually synonymized with H. matthwei because of their 2009; Koufos and Konidaris 2011). size similarity (Forstén and Garevski 1989; Zhouhri and The various skeletal and dental characters of H. mace- Bensalmia 2005). The main problem for this confusion, in donicum confirm the habitat change from Vallesian to my opinion, is the unknown taxonomic status and locality Turolian. The Vallesian form of H. macedonicum is larger of H. matthwei. This taxon is only based on the holotype with rich enamel plication and more robust metapodials hav- (skull and associated mandible from Samos); as it was men- ing more lateral mobility or in other words less expressed tioned above some skulls from Q5 of Samos referred to H. running character in the legs (Figs. 12, 13) than the Turolian matthewi belong to H. nikosi or H. cf. dietrichi (Vlachou one, characters indicating relatively less open and dry hab- 2013). On the other hand, there are several fossiliferous itat. In such an environment the soft food (fresh grasses, sites in Samos which belong to different stratigraphic lev- leafs) is more abundant and thus the plication number in the els with different age (Koufos et al. 2009b) and it is im- Vallesian form of H. macedonicum is higher than that of possible to correlate the holotype of H. matthewi to them. the Turolian one (Fig. 12). In contrast, the Turolian form of Besides these problems the comparison of the RPl skull of H. macedonicum is smaller with less enamel plication, and H. macedonicum with the holotype of H. matthwei indicated more slender metapodials with less lateral mobility than the several morphological differences distinguishing the two Vallesian one, suggesting a lightweight form running in the taxa. The distinction of the two species was also clear from open landscape and feeding on the grass floor. the study of some skull remains of H. macedonicum from Hipparion macedonicum is reported as a member of the the early Turolian locality NIK described recently (Koufos “Cremohipparion”-group which includes a number of taxa and Vlachou 2016). Bernor et al. (1996) and Vlachou (2013) (Bernor et al. 1996). According to these authors H. macedon- considered that H. matthewi originates from H. macedoni- icum is considered as sister-taxon of H. moldavicum which cum; moreover the last author suggested that H. matthewi of originates from the primitive H. primigenium group. Vlachou Samos and Asia Minor originated from a late Vallesian form (2013) placed H. macedonicum in the H. macedonicum-mor- of H. macedonicum which migrated in this area and adapted KOUFOS—LATE MIOCENE HORSES FROM GREECE 535 to the local conditions. This approach is possible but the Bonis, L. de, Bouvrain, G., Geraads, D., and Koufos, G.D. 1992. Diversity limited material from Samos cannot complete the scheme. and palaeoecology of Greek late Miocene mammalian faunas. Palaeo- geography, Palaeoclimatology, Palaeoecology 91: 99–121. Considering the name H. matthwei, I propose to keep it only Cande, S.C. and Kent, D.V. 1995. Revised calibration of the geomagnetic for the holotype until to find more material in Samos or in polarity time scale for the late Cretaceous and Cenozoic. Journal of Asia Minor for certain comparisons and taxonomic results. Geophysical Research 100: 6093–6095. The study of the entire material of H. macedonicum Eisenmann, V. 1988. Contributions à l ètude du gisement Miocène supérieur suggests that the Vallesian form of the taxon differs from de Montredon (Herault). Les grands mammifères. 5. Les Perissodac- tyles, Equidae. Palaeovertebrata, special volume 1988: 65–96. the Turolian one. The comparison of the two forms indi- Eisenmann, V. 1995. What metapodial morphometry has to say about some cates that the first is characterized by large size, short narial Miocene hipparions. In: E.S. Vrba, G.H. Denton, T.C. Partridge, and opening (the nasal notch is retracted above the middle of L.H. Burckle (eds.), Palaeoclimate and Evolution with Emphasis on the C-P2 diastema), long tooth rows, rich enamel plication, Human Origins, 48–162. Yale University Press, New Haven. elongated and narrow plis, relatively robust metapodials and Eisenmann, V. and Sondaar, P.Y. 1998. Equidae. In: S. Sen (ed.), Plio- cene Vertebrate Locality of Çalta, Ankara, Turkey. Geodiversitas 20: less running legs. The Turolian form is small with relatively 409–439. elongated narial opening (the nasal notch retracted above Eisenmann, V., Alberdi, M.-T., Giuli, C. de, and Staesche, U. 1988. Meth- the P2), short tooth rows, low enamel plication with short odology. In: M. Woodburne and P.Y. Sondaar (eds.), Studying Fossil and wide plis, slender metapodials and running legs. This Horses, 1–71. E.J. Brill press, Leiden. morphology reflects the habitat of both forms which was Eronen, J.T, Attaabadi, M.M., Michels, A., Karme, A., Bernor, R.-L., and Fortelius, M. 2009. Distribution history and climatic controls of the more open, dry and warm during the Turolian, an approach Late Miocene Pikermian chronofauna. Proceedings of the National agreeing well to the known palaeoecological results based Academy of Sciences of the U.S.A.106: 11867–11871. on various methods and indicators. Forstén, A.M. 1968. Revision of the Palearctic Hipparion. Acta Zoologica Fennica 119: 1–134. Forstén, A.M. 1997. A review of Central Asiatic hipparions (Perissodacty- Acknowledgements la, Equidae). Acta Zoologica Fennica 205: 1–26. Forstén, A.M. and Garevski, R. 1989. Hipparions (Mammalia, Perissodac- The last excavations in Axios Valley were supported by the Research tyla) from Macedonia, Yugoslavia. Geologica Macedonica 3: 159–206. Committee of the Aristotle University of Thessaloniki (Project no. Gromova, V. 1952. Le genre Hipparion. 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